Music and liturgy can assist or express a worshipping heart, but they cannot make a non-worshipping heart into a worshipping one. The danger is that they can give a non-worshipping heart the sense of having worshiped. So the crucial factor in worship in the church is not the form of worship, but the state of the hearts of the saints. If our corporate worship isn’t the expression of our individual worshipping lives, it is unacceptable.
John MacArthur in Jerry Bridges, The Joy of Fearing God, p. 240
Life Is Worship 
What a profound quote.
What I like about the quote is that MacArthur doesn’t say that style of worship is unimportant, but if the heart isn’t right, no style of worship is acceptable — period!